mm/mm_init: use helper macro BITS_PER_LONG and BITS_PER_BYTE

It's more readable to use helper macro BITS_PER_LONG and BITS_PER_BYTE. 
No functional change intended.

Link: https://lkml.kernel.org/r/20230807023528.325191-1-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/mm_init.c

@@ -79,7 +79,7 @@ void __init mminit_verify_pageflags_layout(void)
 	int shift, width;
 	unsigned long or_mask, add_mask;
 
-	shift = 8 * sizeof(unsigned long);
+	shift = BITS_PER_LONG;
 	width = shift - SECTIONS_WIDTH - NODES_WIDTH - ZONES_WIDTH
 		- LAST_CPUPID_SHIFT - KASAN_TAG_WIDTH - LRU_GEN_WIDTH - LRU_REFS_WIDTH;
 	mminit_dprintk(MMINIT_TRACE, "pageflags_layout_widths",
@@ -1426,9 +1426,9 @@ static unsigned long __init usemap_size(unsigned long zone_start_pfn, unsigned l
 	usemapsize = roundup(zonesize, pageblock_nr_pages);
 	usemapsize = usemapsize >> pageblock_order;
 	usemapsize *= NR_PAGEBLOCK_BITS;
-	usemapsize = roundup(usemapsize, 8 * sizeof(unsigned long));
+	usemapsize = roundup(usemapsize, BITS_PER_LONG);
 
-	return usemapsize / 8;
+	return usemapsize / BITS_PER_BYTE;
 }
 
 static void __ref setup_usemap(struct zone *zone)